1. Field of the Invention
This invention relates to feeding material into packages or pouches and more particularly to apparatus and methods for measuring and dispensing one or more individual product components for feeding into pouches wherein at least one or more of the components is of relatively small volume.
2. Description of Prior Art
Packaging of powdered or particulate products into pouches for distribution, sale and consumer use has typically been accomplished, for example, by feeding a series of open-ended pouches around a filling wheel where the pouches are held open for filling. A plurality of spouts is mounted for rotation with the filling wheel and above the pouches. A metering apparatus is mounted above the rotating spouts for dropping product into the spouts and thence into pouches. The spouts rotate in a plane intersecting the plane of rotation of the filling wheel, such that spouts rotate down into the pouches in a filling area of the run of pouches about the filling wheel. Product is dropped through the spouts in this area and into the pouches. Multiple feeders have been used to feed relatively large quantities of different products into the pouches. Examples of apparatus for such prior filling operations are shown in U.S. Pats. Nos. 3,821,873; 4,232,504; 4,344,269; 4,702,289; 4,848,421; 5,060,450 and 5,320,146. Each of these is herewith incorporated by reference as if fully set forth herein.
Pouches are used to package products of various nature and use. For example, a homogeneous blend of components can be dispensed into a pouch for use where a portion of the product is used at one time while the remainder is used at a later time. This typically requires suitable component blending prior to pouch filling so that any portion of product removed is a homogeneous blend and any portion left over is also a homogeneous blend. In such applications, the product components are pre-blended and the total desired product weight accurately dispensed into the pouch.
Another pouch application is known as the "single-serve" package, where each pouch contains a product, all of which is used at the same time. In such a single purpose application, it is sometimes desirable to feed the individual components of the product mix into the pouch separately from the feeding process of other product components introduced into the pouch. Each component can thus be individually and accurately weighed and dispensed.
Lack of homogeneity in the product components in the single-serve pouch is of no factor since in a single serve application, the entire product fill is used at the same time. Such single service pouches may be found in the packaging of food mixes or pharmaceuticals, as well as in other applications.
In the instance where individual or combined components of a product are to be dispensed separately into a pouch singly or together with other components to make up a full product fill, the desired quantity of one or all of the separately fed components may be very small, and the accuracy of the amount by volume fed into the pouch is important. For example, in a pharmaceutical single serve dose, the active ingredient of a single pouch, or the small total dose, may comprise only a very small volume, and it is very important to accurately meter that small amount. Such small amounts are very hard to meter and dispense accurately and quickly on existing pouch filling apparatus for several reasons. This inability to accurately dispense very small quantities quickly limits the range of use of systems feeding separate components into pouches.
One of the reasons leading to difficulty in measuring and dispensing small product doses is the light density of a product. Another is that the prior dispensing units, such as those shown in the above-referenced patent disclosures, have inherent machine parameters which do not permit the accurate, fast dispensing of small volumes of product. For example, several of the patents disclose a series of volumetric metering cups mounted in a wheel beneath a scraper plate. Product is dropped onto the spinning plate and plows or brushes guide it over the volumetric measuring cups, filling them. See, for example, U.S. Pat. No. 4,848,421. While this works well in many applications, it is not suitable for measuring or dispensing small doses or portions of lightweight product components of less than one gram, for example, which translates into, for example, about one cc volume or even less. The manufacturing tolerances required for accurate, multiple piece cups of such small size would render the apparatus too inaccurate, even if useful cups of such small size could be made. The tolerances for very small volumes are so small that the two piece elongated cups do not repeatedly produce acceptable measure
Another apparatus is shown in U.S. Pat. No. 5,320,146 wherein there are no "cups", per se, however, the metering wheel is provided with angled bores having inlet ports in the upper surface for receiving product and radial outlet ports for discharge. Product is scraped or plowed into the inlet ports and the bores which provide measured product quantities of a single product.
While the bore volume can be adjusted by various means such as sleeves, the bore length is difficult to shorten due to the geometry or configuration of the wheel. Thus, while the bore diameter can be reduced by sleeving, for example, such changes reduce the ratio of the cross-sectional area of the inlet port and/or bore to the overall chamber length. It is difficult to fill and discharge a relatively elongated, small cross section bore with a small volume of a lightweight product at desirable speeds of, for example, 500 bores filled per minute.
Another difficult problem to overcome arises from product which is susceptible to static electricity. Static electricity is generated by the relative motion of the brush or plow against the product on the metering wheel surface, or by the product rubbing against itself. Such static can turn the product particles or granules into what are, in effect, small magnets, adhering to each other and not flowing. This makes it difficult if not impossible to feed small doses or product since the product tends to agglomerate together, or on machine surfaces, rather than flow, even where the machine surfaces are electrically grounded.
Accordingly, it has been one object of the invention to provide improved apparatus and methods for accurately and repeatedly metering small volumetric amounts of product and for dispensing metered product into pouches.
In another aspect of the invention, it is also desirable to be able to adjust metered amounts of product precisely in order to produce accurate doses. Product density may vary with product lot or with weather, for example, and it is desirable to accommodate such changes by adjusting the metering chamber. Where, however, the metering chamber is very small to begin with, it is difficult and expensive to provide chamber volume adjustment.
Moreover, it is also desirable to be able to adjust the volumetric size of the metered dose on the fly, that is with the metering or feeding apparatus running. At the same time, it is desirable to eliminate relative motion between adjustment parts due to normal machine movement which would tend to wear the adjustment components of the feeder, and run them out of tolerance.
In the past, it has been known to use a rotating disc provided with fixed bores defining measuring chambers where the disc thickness defines the chamber length. The disc rotated under a hopper dropping seeds, for example, into the bores. The seeds were dropped from the bores on rotation of the disk. While such discs have been used on the order of about 1/4 inch thick, and with bores about 1/4 to 3/8 inch in diameter, for feeding seeds, for example, such measuring chambers were not adjustable in volume.
Thus, it has been a further objective to provide a small dose volumetric feeder having adjustable metering capacity and to provide a small dose volumetric feeder with an adjustable metering capacity operable on the fly.